Electronic device

Abstract

This electronic device comprises: a first antenna 20 and a second antenna 30 that each perform wireless communications; and a conductive member 40 that is electrically connected to the ground of a circuit built into the electronic device and has a rod-shaped portion of which the tip is an open end that is not electrically connected to another conductive member, wherein the conductive member 40 having the rod-shaped portion is disposed at an intermediate position between the first antenna 20 and the second antenna 30 such that the rod-shaped portion extends in a direction intersecting a direction in which the first antenna 20 and the second antenna 30 are connected.

Description

electronic equipment

[0001] The present invention relates to an electronic device equipped with an antenna for wireless communication.

[0002] There are known electronic devices that can be connected to other communication devices wirelessly, such as those that use wireless LAN communication based on the IEEE 802.11 standard or wireless communication based on the Bluetooth (registered trademark) standard. Such electronic devices are equipped with antennas for wireless communication.

[0003] Some of the electronic devices mentioned above are equipped with multiple antennas that perform wireless communication in the same frequency band. When multiple antennas are present, there is a risk that these antennas will interfere with each other due to electromagnetic waves emitted by each antenna and radiated currents propagating through the ground, adversely affecting wireless communication. Therefore, when multiple antennas are installed, it is necessary to suppress interference and improve isolation between the antennas.

[0004] The present invention has been made in consideration of the above circumstances, and one of its objects is to provide an electronic device that can improve isolation between a plurality of antennas.

[0005] An electronic device according to one aspect of the present invention comprises a first antenna and a second antenna, each of which performs wireless communication, and a conductive member having a rod-shaped portion electrically connected to the ground of a circuit built into the electronic device and having an open end at its tip that is not electrically connected to other conductive members, wherein the conductive member having the rod-shaped portion is positioned at an intermediate position between the first antenna and the second antenna so that the rod-shaped portion extends in a direction that intersects with the direction connecting the first antenna and the second antenna.

[0006] FIG. 1 is a perspective view showing components built into an electronic device according to a first embodiment of the present invention. FIG. 2 is a view showing a state in which a conductive member included in an electronic device according to the first embodiment of the present invention is viewed from the side. FIG. 3 is a perspective view showing components built into an electronic device according to a second embodiment of the present invention. FIG. 4 is a plan view showing components built into an electronic device according to the second embodiment of the present invention. FIG. 5 is a graph showing the directivity of a first antenna according to the second embodiment of the present invention. FIG. 6 is a graph showing isolation between a first antenna and a second antenna according to the second embodiment of the present invention. FIG. 7 is a perspective view showing components built into an electronic device according to a modified example of the present invention. FIG. 8 is a view showing a state in which a conductive member included in an electronic device according to another modified example of the present invention is viewed from the side. FIG. 9 is a view showing a state in which a conductive member included in an electronic device according to another modified example of the present invention is viewed from the side.

[0007] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0008] [First Embodiment] An electronic device 1a according to a first embodiment of the present invention is, for example, a personal computer, a stationary game console, a portable game console, a smartphone, or the like, and includes a substrate 10 and two antennas, a first antenna 20 and a second antenna 30. Fig. 1 is a perspective view showing the substrate 10 built into the electronic device 1a and some of the components connected to the substrate 10.

[0009] The substrate 10 is an electronic circuit board on which various circuit elements for realizing the functions of the electronic device 1a are mounted. In this embodiment, the substrate 10 has a rectangular flat plate shape in a plan view, as shown in FIG. 1 . For ease of explanation, the horizontal direction of the substrate 10 is defined as the X-axis, the vertical direction as the Y-axis, and the substrate 10 is disposed parallel to the XY plane. The direction perpendicular to the substrate 10 is defined as the Z-axis, the direction toward the front side of the substrate 10 is defined as the positive Z-axis direction, and the direction toward the back side of the substrate 10 is defined as the negative Z-axis direction.

[0010] A ground pattern is formed on the conductive layer of the substrate 10. This ground pattern functions as a ground that maintains the reference potential of the electronic circuit mounted on the substrate 10. Hereinafter, the ground of the electronic circuit mounted on the substrate 10 will be referred to as ground G.

[0011] The first antenna 20 and the second antenna 30 are both circuit elements that allow the electronic device 1a to perform wireless communication with other communication devices. In this embodiment, the first antenna 20 and the second antenna 30 perform wireless communication independently of each other, but at least a portion of the frequency bands used for wireless communication overlap. Hereinafter, the representative frequency of the frequency band commonly used for wireless communication by the first antenna 20 and the second antenna 30 is denoted by fx, and the wavelength corresponding to this representative frequency fx is denoted by λx. The representative frequency fx may be, for example, the median value of the frequency range in which the frequency bands used by the first antenna 20 and the second antenna 30 overlap.

[0012] The first antenna 20 is configured as a separate and independent member from the substrate 10. More specifically, the first antenna 20 is formed of a thin, plate-shaped, conductive metal member. A coaxial cable (not shown) is connected to the first antenna 20, and wireless signals transmitted and received by the first antenna 20 to and from external communication devices via wireless communication are transmitted via this coaxial cable. The inner conductor of the coaxial cable is connected to the feed point of the first antenna 20, and the outer conductor is connected to the ground portion of the first antenna 20. As a result, the ground of the first antenna 20 is shared with the ground G.

[0013] The first antenna 20 includes a main body 21 oriented parallel to the XZ plane, and a connecting portion 22 connected to the upper end of the main body 21 so as to be approximately perpendicular to the main body 21 and oriented parallel to the XY plane. The connecting portion 22 is arranged so as to overlap the surface of the substrate 10, and is connected to the substrate 10 by screws or the like. This physically fixes the first antenna 20 to the substrate 10. Hereinafter, of the four sides that form the outer periphery of the substrate 10, the side to which the first antenna 20 is connected will be referred to as side S1. Here, side S1 is the side on the negative Y-axis direction oriented along the X-axis direction.

[0014] Furthermore, the connecting portion 22 is arranged to be in contact with and electrically connected to the ground pattern on the surface of the substrate 10. This allows the ground of the first antenna 20 to be electrically connected to the ground G not only through the coaxial cable described above, but also via the connecting portion 22. Therefore, the ground of the first antenna 20 can be made more stable compared to when the first antenna 20, which is made up of a member independent of the substrate 10, is connected to the circuit on the substrate 10 only by the coaxial cable.

[0015] The second antenna 30 is a pattern antenna formed on the conductive layer of the substrate 10. The second antenna 30 is disposed near one of the four sides that form the periphery of the substrate 10, adjacent to side S1. Hereinafter, of the sides that form the periphery of the substrate 10, the side on which the second antenna 30 is disposed will be referred to as side S2. Here, side S2 is the side on the positive X-axis direction that is oriented along the Y-axis direction. Since the second antenna 30 is formed on the substrate 10, its ground is electrically connected directly to ground G on the substrate 10.

[0016] A screw 40 is disposed at a midpoint between the first antenna 20 and the second antenna 30. The screw 40 is a conductive member made of a conductive material such as iron, and may be a member for fixing the substrate 10 to a structure such as the housing of the electronic device 1a. The screw 40 is fixed near the side S1 of the substrate 10.

[0017] 2 is a diagram schematically illustrating a state in which a screw 40 fixed to a substrate 10 is viewed from the side. As shown in the figure, the screw 40 is arranged so that the head 41 is located on the front surface side of the substrate 10 and the body 42 passes through a through-hole 11 provided in the substrate 10 and faces in the negative direction of the Z axis. The bottom surface 41a of the head 41 is in contact with and electrically connected to the ground pattern of the substrate 10. In other words, the screw 40 is connected to ground G near the end on the head 41 side.

[0018] 2, the body 42 of the screw 40 is fixed to a screw receiver 45. The screw receiver 45 is made of a dielectric material such as an insulating resin. Therefore, the tip 42b of the body 42 of the screw 40 is not electrically connected to any other conductive member and is an open end.

[0019] As described above, the screw 40 is disposed between the first antenna 20 and the second antenna 30, and is particularly disposed closer to the first antenna 20 than the second antenna 30. The screw 40 is also disposed so that the main body 42 extends in a direction (here, the Z-axis direction) that intersects with the direction from the first antenna 20 toward the second antenna 30. By disposing the screw 40, which is a conductive member having a rod-shaped portion, near the first antenna 20 in this manner, the screw 40 functions as a kind of reflector for the electromagnetic waves radiated from the first antenna 20, and exhibits a directivity control effect that changes the directivity of the first antenna 20. This makes it possible to improve the isolation between the first antenna 20 and the second antenna 30.

[0020] In order for the screw 40 to have the effect of changing the directivity of the first antenna 20 in this manner, it is preferable that the spatial distance from the position on the tip side of the first antenna 20 closest to the screw 40 to the screw 40 (i.e., the shortest distance d1 connecting the first antenna 20 and the screw 40) be λx / 4 or less. Furthermore, it is preferable that the electrical length Le of the portion of the screw 40 that protrudes from the position where it is connected to the ground G (bottom surface 41 a) (hereinafter referred to as the stub portion) be a length not less than (1 / 8)λx and not more than (3 / 8)λx, and more preferably a length closer to λx / 4.

[0021] Furthermore, in this embodiment, the grounds of the first antenna 20 and the second antenna 30 are electrically connected to the ground G. Therefore, radiation currents propagating via the ground G can also cause mutual interference between the first antenna 20 and the second antenna 30. The screw 40 functions as a stub to reduce the influence of such interference caused by radiation currents, thereby contributing to improving the isolation between the first antenna 20 and the second antenna 30.

[0022] Specifically, as described above, the screw 40 is electrically connected to the ground G by contacting the bottom surface 41a of its head 41 with the ground pattern of the circuit board 10. The body 42 of the screw 40 has a shape that protrudes from this contact position, and this protruding portion does not contact other conductive members, making it an electrically open end. This makes the body 42 of the screw 40 the stub portion described above, and its surface provides a path along which the radiation current propagating through the ground pattern of the circuit board 10 flows in a detour. As described above, the electrical length Le of this stub portion is equal to or greater than (1 / 8)·λx and equal to or less than (3 / 8)·λx. Therefore, the propagation of radiation current, particularly of wavelengths near λx, can be suppressed at the position of the screw 40.

[0023] The stub portion is a rod-shaped conductive member (here, screw 40) that has a directivity control function and that protrudes beyond the portion electrically connected to ground G, and is a rod-shaped portion that is not electrically connected to other conductive members. Hereinafter, the physical length of the stub portion will be represented as L, and the electrical length as Le. In this embodiment, the entire body portion 42 of the screw 40 functions as the stub portion, and the length of the body portion 42, i.e., the length from the bottom surface 41 a of the head portion 41 to the tip portion 42 b of the body portion 42, is approximately equal to the length L of the stub portion.

[0024] As mentioned above, the electrical length Le of the stub portion of the screw 40 is preferably close to λx / 4. The electrical length Le of the stub portion is approximately equal to the actual length L if the stub portion is placed in air and not in contact with anything. However, if the surface of the stub portion is in contact with a dielectric, the electrical length Le of that portion will be longer than the actual length depending on the dielectric constant of the dielectric. Specifically, if a portion of the stub portion with length Lx is in contact with a dielectric with a dielectric constant ε, the electrical length Le of that portion will be √ε times the length Lx. Therefore, the larger the portion in contact with the dielectric, the shorter the physical length of the main body portion 42 of the screw 40 required to suppress radiation current of the same wavelength can be.

[0025] In this embodiment, as described above, the screw 40 is fixed to the screw receiver 45, which is made of a dielectric material. The screw receiver 45 has a screw hole 45a that engages with the screw 40. The screw 40 is fastened to the screw receiver 45 with the substrate 10 sandwiched therebetween, and is thereby fixed to the substrate 10. The screw receiver 45 makes the electrical length Le of the body 42 of the screw 40 longer than the physical length L.

[0026] Furthermore, the screw receptacle 45 is a member fixed to the housing of the electronic device 1a or the like. As a result, the screw 40 also serves to fix the substrate 10 built into the electronic device 1a to the housing of the electronic device 1a. In other words, by locating the screw 40 at a midpoint between the first antenna 20 and the second antenna 30 and setting the length L of its stub portion to a length corresponding to the wavelength of the electromagnetic waves used in wireless communication, the screw 40 used to fix the substrate 10 can be given the function of improving the isolation between the first antenna 20 and the second antenna 30. Therefore, the isolation between the first antenna 20 and the second antenna 30 can be improved without attaching any other extra structures.

[0027] Furthermore, the effect of improving isolation can be further enhanced by making the electrical length d2 of the propagation path of the radiation current from the position where the screw 40 contacts the ground pattern to the feed point P of the first antenna 20 close to an odd multiple of λx / 2. Specifically, it is preferable to position the screw 40 at a position where the electrical length d2 satisfies the following equation (1), where n is an integer greater than or equal to 0: d2 = (½ + n) λx ± (⅛) λx (1) Note that the propagation path of the radiation current here is assumed to be a path that follows the outer periphery of the conductive member that constitutes the ground G.

[0028] This is because, when the electrical length d2 is close to an odd multiple of the half wavelength in question, it is expected that the phase of the current propagating from the power supply part of the first antenna 20 to the screw 40 via the ground G will lag by approximately 180° relative to the current excited in the screw 40 as it propagates through the air from the first antenna 20 to the screw 40. In this way, the current propagating through the air and the current of opposite phase propagating via the ground G are combined and cancel each other out, thereby suppressing the radiation current propagating from the screw 40 in the opposite direction to the first antenna 20 (i.e., the second antenna 30 side), and improving the isolation between the first antenna 20 and the second antenna 30.

[0029] As described above, according to the electronic device 1a of this embodiment, by placing the screw 40 near the first antenna 20, the directivity of the first antenna 20 can be changed and the propagation of the radiation current generated between the first antenna 20 and the second antenna 30 can be suppressed, thereby improving the isolation between the first antenna 20 and the second antenna 30.

[0030] In the above description, the screw 40 is used to fix the board 10 to the housing of the electronic device 1a. However, this is not limiting, and the screw 40 may be used to fix another structure, such as a shield, to the board 10. Furthermore, the screw 40 may be used to fix another conductive member that is electrically connected to the ground pattern of the board 10 and forms the ground G. An example of such an embodiment will be described below as a second embodiment.

[0031] Second Embodiment An electronic device 1b according to a second embodiment of the present invention will be described below with reference to Figures 3 and 4. In the following description, components that perform the same functions as those in the first embodiment will be given the same reference numerals, and detailed description thereof will be omitted.

[0032] Fig. 3 is a perspective view showing the substrate 10 built into the electronic device 1b according to this embodiment and some of the components connected to the substrate 10. Fig. 4 is a plan view showing the components shown in Fig. 3 as viewed from above (the positive Z-axis direction).

[0033] In this embodiment, the substrate 10 has a substantially rectangular shape in plan view, similar to the first embodiment, and is disposed parallel to the XY plane. The second antenna 30 is formed along a side S2 parallel to the Y axis.

[0034] On the other hand, the first antenna 20 is not directly connected to the substrate 10, but is connected to another conductive member 50. This conductive member 50 may be, for example, a member that functions as a shield to electrically protect other members.

[0035] Specifically, the conductive member 50 is a plate-shaped member made of a conductive metal material and has a substantially rectangular shape in a plan view. The rear side (positive Y-axis direction) of the conductive member 50 overlaps with the substrate 10 in a plan view and is connected to the edge S1 of the substrate 10. This allows the conductive member 50 to contact and be electrically connected to the ground pattern on the surface of the substrate 10. The first antenna 20 is connected to the front end (negative Y-axis direction) of the conductive member 50. The first antenna 20 is positioned such that the distance d3 between its main body 21 and the conductive member 50 in a plan view is λx / 4 or less. This allows the conductive member 50 to constitute part of the ground G. As in the first embodiment, in this embodiment, the ground portion of the first antenna 20 is electrically connected to the ground pattern of the substrate 10 via the conductive member 50.

[0036] In this embodiment, a cooling fan 60 is disposed adjacent to the substrate 10 and the conductive member 50. The cooling fan 60 is a component for cooling circuit components and the like within the housing of the electronic device 1. The cooling fan 60 has a generally cylindrical shape overall and is configured to include at least a fan body 61 and a cover 62 disposed on the surface side of the fan body 61 on the substrate 10 (the positive Z-axis side). The fan body 61 rotates about a rotation axis along the Z-axis, thereby blowing air over and cooling the circuit components and the like within the housing.

[0037] The cover 62 is a member for supporting and protecting the fan body 61, and is made of a conductive metal material, similar to the conductive member 50. The cover 62 has a disk shape and is disposed on the positive Z-axis side of the fan body 61 in an orientation parallel to the XY plane so as to cover the fan body 61. Furthermore, in this embodiment, the cover 62 is connected to a position on the side S1 of the substrate 10 by a plurality of screws 63, and is electrically connected to the ground pattern on the surface of the substrate 10 via these screws 63. Thus, similar to the conductive member 50, the cover 62 also constitutes part of the ground G.

[0038] Furthermore, screws 40 are used to secure the cover 62 to the interior of the housing of the electronic device 1b. That is, in this embodiment, the screws 40 are arranged along the Z-axis direction so as to pass through through holes provided in the cover 62, and the screws 40 are screwed into screw receivers (not shown) made of an insulating material such as resin. As in the first embodiment, the screw receivers may be structures fixed to the housing of the electronic device 1b. The screws 40 and the aforementioned screws 63 secure the cover 62 to the substrate 10 and within the housing of the electronic device 1b. As a result, the screws 40 are electrically connected to the cover 62, which constitutes part of the ground G.

[0039] In this embodiment, as in the first embodiment, the screw 40 is spatially disposed at a midpoint between the first antenna 20 and the second antenna 30, and is disposed at a position where the shortest distance d1 from the first antenna 20 to the screw 40 is equal to or less than λx / 4. This allows the screw 40 to function as a reflector for the first antenna 20, and has the effect of changing the directivity of the first antenna 20.

[0040] 5 is a graph showing the results of simulation-based measurement of the directivity of the first antenna 20. In this figure, the solid line indicates the measurement results in this embodiment, and the dashed line indicates the measurement results for a comparison in the absence of the screw 40. The dashed-dotted circle in this figure indicates the measurement results in the direction in which the screw 40 and the second antenna 30 are located as viewed from the first antenna 20. As shown in the figure, when the screw 40 is located, the gain of the first antenna 20 in the direction in which the screw 40 is located is smaller than when the screw 40 is not located.

[0041] Furthermore, the bottom surface 41a of the head 41 of the screw 40 is electrically connected to the cover 62, and as a result, the body 42 of the screw 40 acts as a stub portion that suppresses the propagation of radiation current, similar to the first embodiment. By setting the electrical length Le of this stub portion to be equal to or greater than (1 / 8)·λx and equal to or less than (3 / 8)·λx, ​​the component of the radiation current with wavelength λx becomes less likely to propagate.

[0042] Furthermore, in this embodiment, the components extending from the feed point P of the first antenna 20 to the screw 40 are electrically connected in this order via the main body 21 of the first antenna 20, the connecting portion 22 of the first antenna 20, the conductive member 50, the ground pattern of the substrate 10, the screw 63, and the cover 62. Therefore, a radiation current propagates from the first antenna 20 to the screw 40 via this path. In this embodiment, the electrical length d2 of the propagation path of this radiation current is close to (5 / 2) λx. This electrical length d2 satisfies the condition for n = 2 in the above-mentioned equation (1). As a result, the current generated in the screw 40 as it propagates through the air from the first antenna 20 to the screw 40 and the opposite-phase current propagating via the ground G are combined and cancel each other out, improving the isolation between the first antenna 20 and the second antenna 30.

[0043] FIG. 6 is a graph showing the results of a simulation of the isolation performance between the first antenna 20 and the second antenna 30 in this embodiment. The horizontal axis of the graph represents frequency, and the vertical axis represents isolation value. The smaller the value, the better the isolation between the antennas (i.e., the less the influence of the first antenna 20 and the second antenna 30 on each other). In this figure, as in FIG. 5 , the solid line represents the measurement results in this embodiment, and the dashed line represents the measurement results in the absence of the screw 40 for comparison. Here, the representative frequency fx commonly used for wireless communication by the first antenna 20 and the second antenna 30 is 2.4 GHz. As shown in the figure, it was confirmed that, in a frequency band including the representative frequency fx, the isolation is improved when the screw 40 is present compared to when it is not present.

[0044] When the screw 40 is fastened to a screw socket formed of a dielectric material as in the first embodiment, the electrical length Le of the main body 42 of the screw 40 becomes longer than the physical length L due to contact with the screw hole provided in the dielectric screw socket. Therefore, the propagation of the radiation current of the target wavelength can be suppressed with a relatively short length L.

[0045] As described above, the screw 40 also serves to fix the cooling fan 60 to the housing of the electronic device 1b, thereby adding the function of improving the isolation between the first antenna 20 and the second antenna 30 to the screw 40 used to fix the cooling fan 60 to the housing of the electronic device 1b, thereby improving the isolation without attaching any other extra structure.

[0046] [Modifications] The embodiments of the present invention are not limited to those described above, and various modifications are possible.

[0047] For example, the shapes and positional relationships of the first antenna 20, the second antenna 30, and the screw 40 are not limited to those described above and may vary within the scope of the invention described in this specification. Furthermore, the elements that make up the ground G and the shapes and positional relationships of each element are not limited to those described above and can be modified in various ways. Below, modified examples of the ground pattern of the substrate 10 that makes up the ground G will be described.

[0048] FIG. 7 shows a modified example of the first embodiment in which a slit 12 is formed in the ground pattern on the surface of the substrate 10. In this example, a slit 12 without a conductive layer is formed in the ground pattern on the surface of the substrate 10 between the position where the first antenna 20 is connected and the position where the screw 40 is fixed. The propagation path of the radiation current from the feed point P of the first antenna 20 to the screw 40 bypasses the slit 12. Therefore, the electrical length d2 of this propagation path is longer than in the first embodiment by the length along the outer periphery of the slit 12. By adjusting the shape and size of the slit 12, the electrical length d2 of the propagation path of the radiation current can be adjusted to satisfy the above-mentioned formula (1). In the example of FIG. 7, the electrical length d2 is close to (3 / 2) λx, which satisfies the condition for n = 1 in formula (1).

[0049] Furthermore, in the above explanation, the screw 40 is electrically connected by being in direct contact with the ground pattern of the substrate 10 or the cover 62, but this is not limited thereto, and the screw 40 may also be electrically connected to a conductive member that constitutes the ground G by capacitive coupling.

[0050] FIG. 8 illustrates an example of such an embodiment, showing the screw 40 as viewed from the side, similar to FIG. 2 . In this example, a dielectric layer 13 is formed on the surface of the substrate 10, and the screw 40 is not in direct contact with the ground pattern of the substrate 10. However, the ground pattern on the surface of the substrate 10 and the bottom surface 41 a of the head 41 of the screw 40 are capacitively coupled via the dielectric layer 13. In this case, similar to the first embodiment, the body 42 protruding from the bottom surface 41 a of the head 41 of the screw 40 functions as a stub. This suppresses the propagation of radiation current with a wavelength corresponding to the electrical length Le of the body 42 of the screw 40. Although omitted from FIG. 8 , the screw 40 may be fixed to a screw socket formed of a dielectric, similar to FIG. 2 .

[0051] In the explanations given so far, in all of the embodiments, the main body 42 of the screw 40 functions as a stub and controls the directivity of the first antenna 20. However, the embodiments of the present invention are not limited to this, and any conductive member that is electrically connected to the ground G and whose positional relationship between the first antenna 20 and the second antenna 30 satisfies a predetermined relationship can be used in place of the screw 40.

[0052] For example, if the screw 40 is fixed to a screw socket formed of a conductor rather than a dielectric, the screw 40 alone will not function as a stub. However, because the main body 42 of the screw 40 comes into contact with the conductor screw socket, the entire assembly including the conductor screw socket can control the directivity of the first antenna 20 and function as a stub.

[0053] FIG. 9 shows an example of such an embodiment. In this example, as in FIG. 2 , the screw 40 is fastened to a screw hole 45a formed in the screw holder 45. However, the screw holder 45 has a rod-like shape and is made of a conductive material, unlike the first embodiment. In this example, the top surface 45b of the screw holder 45 contacts the back surface of the substrate 10. Therefore, it is the surface portion of the screw holder 45 that protrudes from the ground G of the substrate 10, which is the propagation path of the radiation current, and functions as a stub portion. In other words, the longitudinal length of the screw holder 45 (the length from the top surface 45b to the bottom surface 45c) is the length L of the stub portion.

[0054] In Figure 9, the screw 40 is used to fix the substrate 10 as in the first embodiment, but this is not limited to this. Even if the screw 40 fixes other conductive members that make up the ground G, such as the cover 62 of the cooling fan 60, the screw holder 45 to which the screw 40 is fastened may also function to control the directionality of the first antenna 20 and as a stub portion.

[0055] The conductive member having a portion that functions as a stub portion may be a positioning boss. Figure 10 is a diagram showing an example of such an embodiment. In the example shown in this figure, a boss 80 passes through a through hole 11 provided in a substrate 10, and the tip of the boss 80 is inserted into a hole 85a provided in a boss holder 85 formed of a dielectric material. This positions the substrate 10 relative to the boss holder 85. Note that, similar to the screw holder 45 in Figure 2, the boss holder 85 is assumed to be a member fixed to the housing of the electronic device.

[0056] In this example, the side of the boss 80 is in contact with the through-hole 11 provided in the substrate 10, thereby electrically connecting the boss 80 to the ground G of the substrate 10. Therefore, the part of the boss 80 that protrudes from the back surface side of the substrate 10 functions as a stub portion. In this case, the length L of the stub portion is the length from the back surface of the substrate 10 to the tip of the boss 80, as shown in the figure.

[0057] As described above, the conductive member having a portion that performs directivity control and functions as a stub may be a member having various shapes and sizes as a whole, but it is preferable that the portion that functions as the stub portion is rod-shaped, and that the length L of the portion that functions as the stub portion (the length from the propagation path of the radiation current to the tip of the portion) in the longitudinal direction is longer than the length in other directions.

[0058] Although the above description describes the arrangement of only one conductive member having a stub portion between the first antenna 20 and the second antenna 30, multiple such conductive members may be arranged. In this case, the electrical lengths of the stub portions of the multiple conductive members may be different from each other, thereby suppressing radiation currents of multiple wavelengths. For example, if the first antenna 20 and the second antenna 30 perform wireless communication in two overlapping frequency bands, and the wavelengths corresponding to these two overlapping frequency bands are wavelengths λx1 and λx2, the isolation of both wavelengths can be improved by arranging two conductive members between the first antenna 20 and the second antenna 30: one conductive member having a stub portion with an electrical length Le corresponding to wavelength λx1, and the other conductive member having a stub portion with an electrical length Le corresponding to wavelength λx2.

[0059] 1a, 1b Electronic device, 10 Board, 20 First antenna, 21 Main body, 22 Connection portion, 30 Second antenna, 40 Screw, 41 Head, 42 Main body, 45 Screw holder, 50 Conductive member, 60 Cooling fan, 61 Fan body, 62 Cover, 63 Screw, 80 Boss, 85 Boss holder.

Claims

1. An electronic device comprising: a first antenna and a second antenna, each of which performs wireless communication; and a conductive member having a rod-shaped portion electrically connected to the ground of a circuit built into the electronic device and having an open end at its tip that is not electrically connected to other conductive members, wherein the conductive member having the rod-shaped portion is positioned midway between the first antenna and the second antenna so that the rod-shaped portion extends in a direction that intersects with the direction connecting the first antenna and the second antenna.

2. An electronic device according to claim 1, wherein the distance between the conductive member having the rod-shaped portion and the first antenna is equal to or less than 1 / 4 of the wavelength commonly used for wireless communication by the first antenna and the second antenna.

3. An electronic device according to claim 1, wherein the electrical length from the position where the conductive member having the rod-shaped portion is connected to the ground of the circuit to the tip is between one-eighth and three-eighths of the wavelength commonly used for wireless communication by the first antenna and the second antenna.

4. An electronic device according to claim 1, wherein the first antenna is fed with power by a coaxial cable, the outer conductor of the coaxial cable is connected to the ground section of the first antenna, and the ground section is further electrically connected to the ground of the circuit via a path separate from the coaxial cable.

5. An electronic device according to claim 1, wherein the ground portion of the first antenna is electrically connected to the ground of the circuit, and the electrical length of a current propagation path from the feed point of the first antenna to the position where the conductive member having the rod-shaped portion connects to the ground of the circuit via the ground of the circuit satisfies (1 / 2+n) λx ± (1 / 8) λx, where λx is a wavelength commonly used for wireless communication by the first antenna and the second antenna, and n is an integer greater than or equal to 0.

6. An electronic device according to claim 1, further comprising a substrate to which the first and second antennas are connected, and the conductive member having the rod-shaped portion is a screw fixed to the substrate.

7. An electronic device according to claim 1, further comprising: a substrate to which the first and second antennas are connected; and another conductive member electrically connected to the ground pattern of the substrate, wherein the conductive member having the rod-shaped portion is a screw fixed to the other conductive member.

8. An electronic device according to claim 7, wherein the other conductive member is a member that constitutes a cooling fan.

9. An electronic device according to claim 6 or 7, wherein the screw is fixed to a screw fastener formed of a dielectric material.

10. An electronic device according to claim 1, further comprising a substrate to which the first and second antennas are connected, a screw is fixed to the substrate, and the conductive member having the rod-shaped portion is a screw holder to which the screw is fixed.

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